Corrosion preventive



Patented Nov. 16, 1948 cormosron PREVENTIVE William S. Davis, J r., Pittsburgh, Pa., and Donald L.-Wright, Westfleld, N. J., assignors to Standard Oil Development Company, a corporation p of Delaware No Drawing. Application August 5, 1944, Serial No. 548,321

1, Claim. (Cl. 2so 23) surfaces and the like during periods of storage and transportation, but the disadvantage inherent in the use of most of these compositions lies in the fact that the vehicle must be disassembled in order to remove the rust preventing agent before operation. This is due to the fact that the composition dries to leave a hard film on the friction surface, or, if non-drying, is of such an oily or lubricative nature that the surface cannot perform its frictional function until the composition is removed. Examples of such compositions are those containing petrolatum and lanolin or heavy lubricating oil and lanolin, cup greases, varnishes containing tung oil, and the like. Other rust preventing compositions have been proposed which contain light lubricating oils as base oils and rust preventing ingredients which would be largely volatilized under conditions of use, as in the application of brakes to the brake drums, but these compositions are of such light and volatile nature that they would be too quickly removed by a slight use of the brakes, and would quickly drain of! under hot weather conditions or be washed off by water.

It is an object of the present invention to prepare a composition which will satisfactorily serve to protect the surfaces of brake drums, frictional clutches and the like during storage, and which will permit a few applications of the brake, for example, at the dockside prior to shipment overseas, without removing the composition, so that the brake drum will be protected during a further period of transporation or storage, e. g., during a voyage overseas; but on further use of the brake will be removed from the brake drum altogether and will not require disassembling. It has been found that this object can be attained by the application of a composition which contains three essential ingredients: (1) a mineral oil base which volatilizes substantially completely below 750 (2) a thickening or viscosity increasing agent which will be completely vaporied at 750 F. and which will impart to the composition a viscosity of about 350 to about 1000 seconds (Saybolt) at 210 F., and which possesses greater 2. adhesivity than conventionally refined oils of similar viscosity, and (3) a corrosion inhibiting material, of which the portion which is non-volatile at 750 F, is not greater in amount than 10% of the entire rust preventing composition.

The base oil chosen will be a mineral oil which has a boiling range substantially-entirely below 750 F., but which will of course be substantially non-volatile at ordinary temperatures. An oil especially adapted for use in preparing the compositions of the present invention is mineral seal oil boiling approximately within the range of 450-620 F.

Among the viscosity increasing agents which may be used to secure satisfactory resistance to moderate use of brake drums and the like the polyalkenes have been found to be particularly useful. These are linear type polymers of the alkenes and are typified by the high molecular weight polymers which are obtainable by polymerizing isobutene at a low temperature, for instance, below 10 C. and preferably below -40 0., with the aid of a catalyst, such as boron fluoride. In their commercial production the polybutenes are essentially derived from isobutene, but varying quantities of normal butenes may be present, also other normal molecular weight hydrocarbons which act as diluents. Other 'isoolefin reactants, e. g., isopentene, may be used to form polymers possessing similar physical and chemical properties. These are in general called polyalkenes. They have a low iodine number and hydrogen-to-carbon ratio of about 2.0, which indicates that on an average no more than one double bond is present in each polymer molecule. The molecules of such polymers contain an unsaturated aliphatic radical and an arrangement which predisposes the molecules to unite into a long chain of carbon atoms, all of which, with a possible exception of a terminal pair of carbon atoms, are saturated and with alternate individual or pairs of carbon atoms in the chain linked to alkyl radicals. Such polymeric homologous compounds, as typifled by the polyalkenes of high molecular weight, whenheated at temperatures above about 570 F. undergo disintegration by scission of the carbon-to-carbon bonds.

A poly-butene product varies in consistency from viscous liquids to tough, elastic solids as the average molecular weight of the polymers increases from about 1000 to 200,000 or higher. It has been found that one of the most satisfactory products for use in connection with the present invention is a polybutene polymer having an average molecular weight of 60,000 to 80,000. Such v a,4ss,ess

a mateial has many properties which make it especially suitable for incorporation. in a rustpreventive for automotive or aircraft brake drums; for example, a 7% solution of this polymer in mineral seal oil is a colorless liquid which is extremely stable against oxidation, has a pour point above 32 F. but does not become hard at extremely low temperatures, has an extremely high viscosity index (above 200), evaporates slowly and completely at temperatures above 400 F., and does not spread rapidly at elevated temperatures.

Practically any desired increase of viscosity in the rust-preventing composition can be obtained by varying the molecular weight and proportion of the polymer incorporated. However, for the purpose of the present invention it is desirable to use such a quantity of the polymer material, preferably a polymer having a molecular weight of 60,000 to 80,000, which will impart to the oil solution a viscosity of about 350 to about 1000 (Saybolt) at 210 F. after allowance for the effect on the viscosity of the corrosion inhibiting ingredients which are introduced.

It should be understood that the invention is not limited to the use of the polyalkenes as agents for increasing the viscosity of the rust-preventing composition. Oxygen-containing polymers, such as Acryloid resins, may, for example, be used. The materials used should be completely vaporized at 750 F. in order that they may be completely removed by the heat caused by application of the brakes a considerable number of times. The material should also have such physical properties as will permit squeezing the material away from the contact surfaces under application of high unit pressures.

The third ingredient of the rust-preventive composition is the corrosion inhibitor. This should be of such a nature that it can be largely removed under the high temperature and high pressure conditions attained in the use of the brake drum, and it should not introduce into the entire composition more than 10% of material boiling above 750 F. One of the most satisfac tory corrosion inhibitors of this type is a mixture of a saponifiable fatty material, such as degree, and an oil soluble alkali metal salt of sulfonic acids formed on treating petroleum oils with concentrated sulfonic acid. The sodium salt of the siilfonic acids is particularly satisfactory. The

ratio of these two materials may range from 1 part by weight of degras to parts by weight of sodium sulfonate salts to 15 parts by weight of degras to 1 part of the salts. Generally, the ratio is from 1 to 2 parts of degras to 1 part of salts. It is convenient to prepare, for example, a mixture containing about 1 part each of degras, dry sodium salts of petroleum sulfonic acids, and pale paramn oil of 100 seconds viscosity (Saybolt) at 210 F., and to incorporate such a mixture in the mineral oil solution of the polybutene. Other materials than the above may be used as the corrosion inhibitor ingredient. For example, one may use a material known as Wecker still bottoms, which are prepared by the low temperature liquid phase catalytic oxidation of paraflin wax or petrolatum. This material may be used alone or in combination with degras, with or without the further addition of alkali salts of petroleum sulfonic acids. I

As an example of the application of the present invention, the preparation and testing of a typical preferred rust-preventive composition will be described in detail.

Example of degras, dry sodium salts of petroleum sulfonic acids and pale paraflin lubricating oil of 100 seconds viscosity (Saybolt) at 210 I. This material was brushed on the surface of the brakedrums of the front two hydraulic brakes of a A ten delivery truck. The truck was taken on the road and eight severe applications on the brake were made to bring the truck to a stop. The brake drums were then examined. It was found that there had been no detrimental effect to the braking operation and the rust-preventive composition had completely disappeared. Also no ill effects were noted on the lining material of the brake drum. A similar test was made by applying the same material to the brake drums of a station wagon, and a similar number of stops were made by severe application of the brake. Bimilarly satisfactory results were observed as to the condition of the brake and brake lining.

It will be understood that the compositions described above may be equally well applied to the braking equipment of other vehicles than automotive trucks and passenger cars. They may be used in tanks, aircraft or railroad cars, or the like, and they may be applied not only to the braking surfaces but to clutch surfaces and in general to any metallic surfaces subject to frictional contact with other surfaces.

This invention is not to be considered as limited by any of the examples which have been mentioned or described above for illustrative purposes only, but is to be limited solely by the terms of the appended claim.

We claim:

A rust preventing composition consisting of (l) a mineral oil base which vaporizes completely below 750 F., (2) a partially volatile corrosion inhlbltor consisting of sodium petroleum sulfonates and dezras in a ratio of one to two .parts of degree to one part of sulfonates, the quantity of such corrosion inhibitor being so proportioned that it is suflicient to prevent corrosion. but is not so great that the unvolatilized residue remaining after being subjected to a temperature of 750 F. exceeds 10% by weight of the total composition, and (3) a polybutene of 60,000 to 80,000 molecular weight, the quantity of said polybutene being so proportioned as to impart to the total composition a viscosity of 350 to 1000 seconds Saybolt at 210 F.

- WILLIAM S. DAVIS, JR.

DONALD L. WRIGHT.

REFERENCES CITED The following references are of record in the .flle of this patent:

UNITED STATES PATENTS Number Name Date 2,093,431 Frolich Sept. 21, 1937 2,182,992 Lebo Dec. 12, 1939 2,336,195 Sparks et al Dec. '7, 1943 2,340,996 Smyers Feb. 8, 1944 

